Hydraulic drilling-machine drive

ABSTRACT

The invention pertains to a hydraulic rotary drive for the rotating rod assembly of a drilling machine which contains at least two hydraulic motors ( 1 - 3 ) with the motor shafts ( 34 - 36 ) that are connected to a common output shaft ( 11 ) by means of a gear, with a clutch ( 4 - 6 ) being arranged between the motor shaft ( 34 - 36 ) of each hydraulic motor ( 1 - 3 ) and the gear such that the rotational movement of each hydraulic motor ( 1 - 3 ) can be disengaged from the rotational movement of the output shaft ( 11 ). The invention aims to develop a highly variable rotary drive for ground and rock drilling machines. According to the invention, this objective is attained due to the fact that: (1) the gear is formed by pinions ( 7 - 9 ) that are each connected to a corresponding motor shaft ( 34 - 36 ) by means of a corresponding clutch ( 4 - 6 ), with said pinions engaging a toothed wheel ( 10 ) arranged on the output shaft ( 11 ), and (2) the housings of the hydraulic motors ( 1 - 3 ) have identical connection dimensions, with the hydraulic motors having different intake volumes.

FIELD OF THE INVENTION

[0001] The invention pertains to a hydraulic rotary drive for the rotating rod assembly of a drilling machine which contains at least two hydraulic motors. The motor shafts of these motors are connected to a common output shaft by means of a gear, with a clutch being arranged between the motor shaft of each hydraulic motor and the gear such that the rotational movement of each hydraulic motor can be disengaged from the rotational movement of the output shaft.

DESCRIPTION OF THE RELATED ART

[0002] The term drilling machine in the sense of the present invention pertains, in particular, to hydraulically driven ground and rock drilling machines which are primarily used in underground working and explosives technology in order to create drilled holes in the ground, in rocks, and in building foundations, as well as to all similar drilling machines with a hydraulic rotary drive, with a drilling rod assembly that is mounted on the output shaft of the rotary drive.

[0003] A rotary drive of this type without a clutch is, for example, known from German Patent DE 40 20 111 C2. This document describes a control unit that operates depending on the pressure for the load-dependent connection of a hydraulic motor to a permanently operating base-load motor. In this rotary drive, both hydraulic motors are continuously connected to a toothed wheel by means of pinions, with the toothed wheel mounted on the output shaft transmitting the rotational movement onto the drilling rod assembly, e.g., a rock drilling machine or an auger. As long as the rotational resistance on the drilling rod assembly is low and only a relatively low torque is required for driving the drilling rod assembly, only one of the two hydraulic motors is charged with operational pressure. The hydraulic connections of the second hydraulic motor are shunted so that this hydraulic motor operates as a pump running in the idle mode and delivers no power.

[0004] Once the torque required for driving the drilling rod assembly exceeds a certain threshold, the second hydraulic motor is actuated in order to boost the first hydraulic motor. This increases the torque applied to the drilling rod assembly, with the rotational speed simultaneously decreasing since the driving pump for the hydraulic circuit of the motors usually has a constant rate of flow.

[0005] This known design is extremely robust with respect to the requirements for ground drilling tools. The gear of the rotary drive is not subjected to wear and only requires little maintenance due to the simple and continuous rotary connection between the motors and the toothed wheel of the output shaft. The idle running of an additional hydraulic motor, which is achieved by shunting its connections, represents a conventional measure which generally does not cause any problems.

[0006] However, practical experience has shown that significant problems arise if hydraulic motors operate as an idle pump at high rotational speeds. The so-called “inter-splashing” of the hydraulic motors influences the total degree of efficiency of the rotary drive due to the volumetric degrees of efficiency of the circuit elements arranged in the hydraulic circuit (valves, etc.) as well as the motors. In addition, this inter-splashing frequently leads to overheating of the hydraulic system after extended periods of time because the power losses are dissipated by the hydraulic medium, and the cooling of the hydraulic fluid is low in comparison to the power loss created by the dissipation of heat. In addition, this drive is limited to two operating modes, namely the base motor by itself or in cooperation with the auxiliary motor.

[0007] DE 44 04 829 C2 discloses a drive that contains a hydraulic motor which can be actuated by a transmission by means of a clutch in addition to a permanently operating hydraulic motor. In addition, a planetary gear is provided in the driven shaft of this drive. Due to the planetary gear, only limited torques can be transmitted, and only two modes (base motor by itself and in cooperation with the auxiliary motor) can be realized due to the constructive prerequisites. This drive is not suitable as a drilling-machine drive that is realized to be robust and to have a small volume.

SUMMARY OF THE INVENTION

[0008] The invention is based on the objective of realizing hydraulic drilling-machine drives with a robust construction and a small volume in the most flexible fashion possible.

[0009] According to the invention, this objective is attained due to the fact that: (1) the gear is formed by pinions that are each connected to a corresponding motor shaft by means of a corresponding clutch, with said pinions engaging a toothed wheel arranged on the output shaft, and (2) the housings of the hydraulic motors have identical connection dimensions, with the hydraulic motors having different intake volumes.

[0010] According to the invention, a reliable gear with a central toothed wheel is used for transmitting the power to the output shaft and the individual pinions on the motor shafts, with a clutch on each motor shaft producing and, when required, disengaging the connection with the pinion. In addition, hydraulic motors with identical connection dimensions and different intake volumes are used. Due to the corresponding connection dimensions, it is possible to realize different motor combinations with the same gear housing, i.e., with a single housing that surrounds the central toothed wheel on the output shaft. The hydraulic motors which can be freely disengaged and which have different intake volumes, i.e., different volumes of a hydraulic fluid that flow through the motor per revolution of the motor shaft, allow a maximum number of different switching positions. In a drive with two hydraulic motors, either motor 1 or motor 2 or both motors can be actuated. If the toothed wheel housing contains three motor connection flanges, seven different switching positions can be realized when using three different intake volumes (motor 1, motor 2, or motor 3 by themselves, motors 1+2, 1+3, and 2+3 together, as well as all three motors simultaneously).

[0011] Since motor housings with corresponding connection dimensions are used, drives with different rotational speed ratios and different torques that drive the output shaft can be realized with the same toothed wheel housing for the central toothed wheel. Depending on the respective requirements, motor combinations can be composed from a series of motors with different intake volumes. Thus, the manufacturer of the rotary drive according to the invention must produce only one variation of the toothed wheel housing and make available a certain number of different hydraulic motors. Depending on the application, the required rotational speed ratio or torque ratio can be composed. Conventional hydraulic motors, e.g., rotary piston motors, can be realized with the same housing connection dimensions and with a broad range of different intake volumes. For example, the intake volumes of a motor series with the same housing connection dimensions might lie between 100 ml per revolution and 1000 ml per revolution.

[0012] The main element of the drive is the housing that surrounds the toothed wheel on the output shaft, with said housing containing several identical flange regions that are used for receiving corresponding clutch flanges. In other words, the first end of the clutch housing is realized in accordance with the motor flange (i.e., complementary to the flange region of the toothed wheel housing), and the second end is realized complementary to the motor flange. Thus, the clutch housing acts similar to an adapter that can be inserted between the complementary flange regions of the toothed wheel housing and the hydraulic motor. The realization of the clutch housing in the form of an adapter provides the advantage that existing drives where the hydraulic motor is directly flanged to the toothed wheel housing can be retrofitted with clutches. In addition, drives with clutch-actuated hydraulic motors, as well as drives with hydraulic motors that permanently act upon the output shaft, can be realized with the same toothed wheel housing. The motor flange is either directly mounted onto the flange region of the toothed wheel housing (permanent connection) or there is a clutch housing arranged in between (clutch-actuated connection).

[0013] In both instances, the flange regions are connected to one another by means of threaded bolts, with the threaded bolts extending through the motor housing and the clutch housing in the case of the clutch-actuated motor. The threaded bolts are advantageously provided with a hexagonal head and screwed into threaded bores arranged in the flange regions of the toothed wheel housing.

[0014] The pinions that are connected to the motor shafts by the clutches are preferably supported in the clutch housing and in the toothed wheel housing by means of axial roller bearings. A cover for simplifying the installation of each bearing should be provided on the side of the toothed wheel housing opposite the flange regions. In this case, a bearing can be mounted in a bearing seat enchanced by the cover.

[0015] In order to connect the hydraulic motors to the driving pump, control valves that are preferably actuated in a hydraulic fashion are provided. In particular, in drilling-machine drives that are arranged on the upper end of a drilling rod assembly which is frequently positioned several meters above the ground, the actuation of a motor may take place at a distance from the drive housing by means of a switching element and hydraulic control pressure lines. In this case, it is not necessary for the person operating the drilling-machine drive to activate control elements on the drive itself in order to actuate the motor.

[0016] It is also sensible to realize the clutch in a hydraulically actuated manner, so that a control pressure line delivers the pressure for closing the clutch simultaneously with the actuation of the auxiliary hydraulic motor. Due to this measure, the clutch is automatically closed when the hydraulic motor that can be disengaged is actuated. Naturally, the clutches can also be actuated in another fashion, e.g., by means of an electromagnetic actuation drive or by means of a pressing spring, in which case the clutch is opened with a suitable disengaging device.

[0017] The actuation of the clutches may take place directly based on the operating pressure of the hydraulic motors. However, a hydraulic circuit that is provided with a separate feed pump and that is not dependent on the operating pressure is preferably provided for delivering the control pressure to the clutch and to the control valves for the operating pressure of the hydraulic motors. Thus, the actuation of the valves and clutches takes place independently of the operating pressure of the motors. In this case, individual hydraulic motors can also be switched on or off for idling motors that are not charged with the operating pressure.

[0018] The clutch is preferably formed by a friction clutch that contains friction linings which can be pressed against one another. In clutches of this type (multi-disk clutches), the clutch linings may either run dry or in a liquid medium. The advantage of such friction clutches can be seen in the fact that the auxiliary hydraulic motor can be switched on while the hydraulic rotary drive is in operation. Temporary differences in the rotational speed of the output shaft and the rotational speed of the hydraulic motor are compensated for by the friction linings that can move relative to one another.

[0019] A hydraulic motor produces a very high torque so that the clutch should be completely closed when the hydraulic motor is charged with pressure. If the friction linings are pressed against each other with an insufficient force, they will slip and may overheat or burn. Generally, the friction linings are pressed against each other with a hydraulically generated pressing force. A reliable load transmission of the clutch is only achieved if the hydraulic pressure for closing the clutch exceeds a certain threshold value. Therefore, a motor may only be charged with pressure if the closing forces acting on the clutch, especially the pressure of the hydraulic fluid closing the clutch exceeds a certain threshold. This threshold lies for example close to 28 bar above atmospheric pressure in a practical embodiment of the clutch.

[0020] Similar to the embodiments described in the German Patent DE 40 20 111 C2 cited above, the hydraulic motors that can be disengaged can also be actuated by means of a suitable automatic device, in particular, if the closing of the clutch is directly coupled to the charging of the corresponding hydraulic motor with pressure.

[0021] The invention also pertains to a hydraulic motor for an above-described hydraulic rotary drive. This motor contains a motor housing and a motor shaft that protrudes out of the axial front end of the motor housing, with the axial front end of the motor housing containing a mounting flange. In order to connect this motor to the central toothed wheel of the rotary drive in accordance with the invention, the rear end of a clutch housing is mounted on the front end of the motor housing, with the front end of the clutch housing containing a mounting flange that corresponds to the mounting flange of the motor housing. As mentioned above, the clutch housing designed in this way is inserted between the flange region of the toothed wheel housing and the motor flange, similar to an adapter.

[0022] A multi-disk clutch that can be hydraulically actuated through a hydraulic connection in the clutch housing is preferably arranged inside the clutch housing. The pinion that is connected to the motor shaft by the clutch preferably protrudes out of the side of the clutch housing opposite the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the invention are described in greater detail below with reference to the figures. The figures show:

[0024]FIG. 1, a hydraulic circuit diagram of a rotary drive according to the invention where all motors are idling;

[0025]FIG. 2, a representation that corresponds to that shown in FIG. 1, with one hydraulic motor being actuated;

[0026]FIG. 3, a representation that corresponds to that shown in FIG. 2, with the same hydraulic motor being actuated in the opposite rotating direction (counter-clockwise rotation);

[0027]FIG. 4, a representation that corresponds to that shown in the previous figures, with all motors being switched on and clockwise rotation;

[0028]FIG. 5, a longitudinal section through a hydraulic motor that is connected to the toothed wheel on the output shaft by a multi-disk clutch while the clutch is open;

[0029]FIG. 6, a representation of the hydraulic motor which corresponds to that shown in FIG. 5, with the multi-disk clutches being closed in this figure, and

[0030]FIG. 7, a combination drawing that shows the individual components of a drive.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The hydraulic rotary drive shown in FIGS. 1-4 contains three hydraulic motors 1, 2, 3 with motor shafts 34, 35, 36 that are each connected to a pinion 7, 8, 9 by a hydraulically actuated clutch with friction linings, namely multi-disk clutches 4, 5, 6. The pinions 7, 8, 9 are rotationally engaged with the toothed wheel 10 on the output shaft 11 of the rotary drive. The drilling rod assembly of a ground drilling machine (not-shown) is connected to the output shaft 11.

[0032] All three motors 1, 2, 3 are connected in a parallel fashion to the pressure lines 12, 13 that are supplied with operating pressure from the driving pump 14 and that allow the hydraulic fluid to flow back from the motors 1, 2, 3 into a reservoir 15. A control valve 16 makes it possible to switch off the motors 1, 2, 3 if the pressure output line 17 of the pump 14 is directly coupled to the return flow line 18 (see FIG. 1) and to realize a change-over between the clockwise rotation (see FIGS. 2 and 4) and counter-clockwise rotation (see FIG. 3).

[0033] A second driving pump 19 generates the control pressure for the control valves 20, 21, 22 that interrupt the hydraulic connection between the pressure lines 12, 13 and the motors 1, 2 and 3 in a first switching position (see FIG. 1) and release said hydraulic connection in a second switching position (see FIG. 4). Manually actuated control valves 23, 24 and 25 connect the control lines 26, 27, 28 to a return flow line 29 leading to the reservoir 15 in a first switching position (FIG. 1) and to a pressure output line 30 of the second driving pump 19 (cf. FIG. 4) in a second switching position. Thus, in this first switching position the hydraulic motor is separated from the pressure supply. It is charged with the pressure of the driving pump 19 in the second switching position.

[0034] Control lines 31, 32 and 33 that form the pressure supply line for the corresponding clutch 4, 5, 6 which can be hydraulically closed are branched off of control lines 26, 27, 28, respectively. A certain pressure threshold must be exceeded for closing the clutches 4,5,6. As long as this pressure threshold is not reached at one clutch 4, 5 or 6, there is a danger that this clutch will slip and it's friction linings will be damaged by the resulting friction heat. Thus, a control device should be present, which cuts the pressure supply to the hydraulic motor 1, 2 or 3 associated to the clutch 4, 5 or 6 as long as the pressure threshold is not reached. For example the restoring spring shown at the control valves 20, 21, 22 in the FIGS. 1 through 4 may be arranged such that they will cut the pressure supply to the motor as long as the pressure, which is present at respective control valve 20, 21 or 22 and which corresponds to the pressure present at the corresponding clutch 4, 5 or 6 is less than the threshold value, which is necessary for completely closing the clutch.

[0035] One can clearly see that arbitrary combinations of the motors 1, 2 and 3 can be connected to the central toothed wheel 10 of the output shaft 11 by selectively actuating the manual control valves 23, 24, 25. The rotating direction of the motors 1, 2, 3 can be adjusted to clockwise or counter-clockwise by means of the control valve 16.

[0036]FIG. 2 shows a control valve 16 that is switched so that the motor rotates clockwise, with only the first driving motor 1 being charged with operating pressure through the pressure lines 12, 13 by means of the control valve 23 and the hydraulically actuated control valve 20. In this case, the clutch 4 is closed due to the control pressure delivered through the control lines 26 and 31.

[0037] In FIG. 3, the control valve 16 is in the opposite switch position (counterclockwise rotation), with only the hydraulic motor 1 being charged with pressure in this case by means of the control valves 23 and 20, and with the clutch 4 being closed.

[0038]FIG. 4 shows the system being switched such that it rotates clockwise, with all three manual control valves 23, 24, 25 conveying a control pressure to the control valves 20, 21, 22 in order to actuate the motors 1, 2, 3 and close the clutches 4, 5, 6.

[0039] In this switch position, the maximum torque is transmitted onto the central toothed wheel 10 at a minimal rotational speed of the hydraulic drive.

[0040] If the motors 1, 2, 3 have different intake volumes, different rotational speeds can be realized with varying maximum torques by individually actuating the motors 1, 2, 3. Different combinations of the driving motors (1+2, 1+3 or 2+3) respectively allow various intermediate torques and rotational speeds. Thus, the rotary drive shown makes it possible to change to seven different rotational speeds with seven different torques on the output shaft 11.

[0041] As an alternative to the described embodiment, known dual motor drives can also be realized in a clutch-actuated fashion. In particular, it is also possible to provide additional motors. Due to the open clutch, these motors do not cause power loss while idling.

[0042]FIGS. 5 and 6 show an embodiment of a hydraulic motor 1 with a clutch that is shown in the opened and closed state, respectively, in these figures. The hydraulic motor 1 consists of a conventional rotary piston motor that generates very high torques (in excess of 1500 Nm). An axially displaceable pressure element 35 is arranged on its motor shaft 34 in a rotationally fixed manner, with said pressure element containing an annular pressure plate 36 that exerts a pressure upon a multi-disk set 37 in the axial direction when the clutch is actuated. Another annular pressure plate 38 is located on the other side of the multi-disk set 37 and connected to a support element 39 that is arranged on one end of the pinion 7 in a rotationally fixed manner by means of a screw connection. The pinion 7 meshes with the toothed wheel 10 that is connected to the output shaft 11 of the rotary drive (cf. FIGS. 1-4).

[0043] The closing of the clutch is realized with a hydraulic piston 40, to the rear side of which hydraulic fluid is conveyed through an inlet bore 41. The piston 40 applies pressure to the pressure element 35 through an axial roller bearing 42. FIG. 5 shows the arrangement with an open clutch. No operating pressure is delivered through the inlet opening 41, and the piston 40 is located in its upper end position, with a definite gap remaining between the pressure plate 36 and the multi-disk set 37. FIG. 6 shows the arrangement with a closed clutch, with the closing pressure being applied to the inlet opening 41 such that the piston 40 is axially displaced toward the toothed wheel 7 and pressure plate 36 is pressed axially against the multi-disk set 37 by the roller bearing 42 and the pressure element 35. Due to the use of a powerful multi-disk clutch, the required torques in excess of 1500 Nm can be transmitted onto the pinion 7. The pinion 7 is supported on roller bearings that are arranged at one end on the front end of the clutch housing 54 and, at the other, opposite the clutch housing 54, in a section of the toothed wheel housing 43 closed with the cover 47. In this case, the cover 47 contains a seat for an axial roller bearing.

[0044]FIG. 7 shows the individual components of a drive, i.e., the three motors 1, 2, 3 and the housing 43 with the central toothed wheel 10 and the flange regions 44, 45, 46 for mounting the three motors 1-3. The three units consisting of hydraulic motors 1-3 and clutches 4-6 are illustrated in a side view of the motor housing 51-53 and the clutch housing 54-56 as well as in a front view, in which the identical front clutch flanges 48 are visible. The housings 51-53 of the three motors 1-3 are essentially identical and may only vary with respect to their structural length. Due to the identical connection dimensions of the three motor housings 51-53, three identical flange regions 44-46 can be provided on the toothed wheel housing 43 even if the intake volumes of the motors vary over broad ranges. In addition, clutches in identical clutch housings 54-56 can be used in connection with the different motors. Each motor 1, 2, 3 forms a unit in connection with a corresponding clutch 4, 5, 6. Each clutch housing 54, 55 or 56 contains a flange 48 that corresponds to the motor housing on its front end. The rear end of each clutch housing 54-56 is realized in accordance with the flange regions 44-46 on the toothed wheel housing. Consequently, a clutch housing 54-56 can be arranged between the flange region 44-46 on the toothed wheel housing 43 and the motor housing 51-53, similar to an adapter. If required, one of the motors 1-3 can be directly flanged to the toothed wheel housing 43 without a clutch.

[0045] Naturally, any existing drive that does not contain clutch-actuated motors can be realized in accordance with the invention by simply inserting a clutch.

[0046] It is preferred that identical clutches 4-6 are used for all motors 1-3. Alternatively, clutches 4-6 with clutch torques that are adapted to the maximum torques of the different motors 1-3 may be used. In this case, the clutch housings 54-56 must retain identical connection dimensions and, if required, only vary with respect to their length.

LIST OF REFERENCE SYMBOLS

[0047]1-3 Hydraulic motor

[0048]4-6 Clutch

[0049]7-9 Pinion

[0050]10 Central toothed wheel

[0051]11 Output shaft

[0052]12 Pressure line

[0053]13 Pressure line

[0054]14 Driving pump

[0055]15 Reservoir

[0056]16 Control valve

[0057]17 Pressure output line

[0058]18 Return flow line

[0059]19 Driving pump

[0060]20-22 Control valve

[0061]23-25 Manual control valve

[0062]26-28 Control line

[0063]29 Return flow line

[0064]30 Pressure output line

[0065]31-33 Control line

[0066]34-36 Motor shaft

[0067]35 Pressure element

[0068]36 Pressure plate

[0069]37 Multi-disk set

[0070]38 Pressure plate

[0071]39 Support element

[0072]40 Piston

[0073]41 Inlet opening, hydraulic connection

[0074]42 Roller bearing

[0075]43 Toothed wheel housing

[0076]44-46 Flange region

[0077]47 Cover

[0078]48 Front clutch flange

[0079]49 Rear clutch flange

[0080]50 Motor flange

[0081]51-53 Motor housing

[0082]54-56 Clutch housing 

We claim:
 1. Hydraulic rotary drive for the rotating rod assembly of a drilling machine, with at least two hydraulic motors (1-3) with motor shafts (34-36) that are connected to a common output shaft (11) by means of a gear, with a clutch (4-6) being arranged between the motor shaft (34-36) of each hydraulic motor (1-3) and the gear such that the rotational movement of each hydraulic motor (1-3) can be disengaged from the rotational movement of the output shaft (11), characterized by the fact that: the gear is formed by pinions (7-9) that are each connected to a corresponding motor shaft (34-36) by means of a corresponding clutch (4-6), with said pinions engaging a toothed wheel (10) arranged on the output shaft (11), and the housings (51-53) of the hydraulic motors (1-3) have identical connection dimensions, with the hydraulic motors having different intake volumes.
 2. Hydraulic rotary drive according to claim 1 , characterized by the fact that the toothed wheel (10) arranged on the output shaft (11) is accommodated in a housing (43) that is provided with flange regions (44-46) that are each used to receive a clutch flange (48).
 3. Hydraulic rotary drive according to claim 1 , characterized by the fact that the clutch (4-6) is arranged in a clutch housing (54-56) with one end that is realized corresponding to the flange (50) of the hydraulic motor (1-3) and with the other end that is realized complementary to the motor flange (50).
 4. Hydraulic rotary drive according to claim 3 , characterized by the fact that threaded bolts extend through each motor housing (51-53) and the clutch housing (54-56) mounted thereon, with said threaded bolts being arranged within the flange region (44-46) of the toothed wheel housing (43).
 5. Hydraulic rotary drive according to claim 1 , characterized by the fact that each pinion (7) meshing with the toothed wheel (10) arranged on the output shaft is supported in the clutch housing (54) and in the housing (43) that surrounds the toothed wheel (10).
 6. Hydraulic rotary drive according to claim 5 , characterized by the fact that a bearing seat which can be enclosed with a cover (54) is arranged on the side of the toothed wheel housing (43) opposite each flange region for a clutch housing (54).
 7. Hydraulic rotary drive according to claim 6 , characterized by the fact that an axial roller bearing is arranged in the cover (47).
 8. Hydraulic rotary drive according to claim 1 , characterized by the fact that each hydraulic motor (1-3) can be charged with hydraulic pressure by a control valve (20-23).
 9. Hydraulic rotary drive according to claim 8 , characterized by the fact that the clutches (4-6) and the control valves (20-23) can be actuated in a hydraulic fashion, with the control line (26-28) for the actuation of a hydraulic motor (1-3) being coupled to the control line (31-33) for closing the clutch (4-6) assigned to this hydraulic motor (1-3).
 10. Hydraulic rotary drive according to claim 1 , characterized by the fact that the hydraulic motors (1-3) are supplied with hydraulic operating pressure by the driving pump (14) through parallel lines.
 11. Hydraulic rotary drive according to claim 1 , characterized by the fact that a hydraulic circuit which is not dependent on the operating pressure of the hydraulic motors (1-3) and which contains a separate driving pump (19) is provided for delivering control pressure to the clutch (4-6) and to the control valves (20-22) for the operating pressure of the hydraulic motors (1-3).
 12. Hydraulic rotary drive according to claim 1 , characterized by the fact that the clutch (1-3) is formed by a friction clutch with coaxial friction linings that can be pressed against one another, in particular, a multi-disk clutch (4, 5, 6).
 13. Hydraulic rotary drive according to claim 12 , characterized by the fact that it comprises a control device, which cuts the supply of hydraulic fluid to one of the hydraulic motors, if the corresponding clutch is not completely closed.
 14. Hydraulic rotary drive claim 13 , characterized by the fact that the clutches are hydraulically actuated and that the control device cuts the supply of hydraulic fluid to one of the hydraulic motors, if the pressure actuating the corresponding clutch does not reach a threshold value.
 15. Hydraulic rotary drive according to claim 1 , characterized by the fact that a control device for the load-dependent actuation of at least one hydraulic motor is provided, with said control device charging a hydraulic motor to be actuated with pressure depending on the operating pressure when a first threshold is exceeded and closing the clutch of the corresponding hydraulic motor, and with the control device disconnecting the hydraulic motor from the operating pressure and opening its clutch if a second threshold is not reached.
 16. Hydraulic motor for a hydraulic rotary drive for the rotating rod assembly of a drilling machine, with a motor housing (51) and a motor shaft (34) that protrudes out of the axial front end of the motor housing (51), with the axial front end of the motor housing (51) containing a mounting flange (50), characterized by the fact that the rear end of a clutch housing (54) is mounted on the axial front end of the motor housing (5 1), with the front end of the clutch housing containing a mounting flange (48) that corresponds to the mounting flange (50) of the motor housing (5 1).
 17. Hydraulic motor according to claim 16 , characterized by the fact that a multi-disk clutch is accommodated in the clutch housing (54).
 18. Hydraulic motor according to claim 16 , characterized by the fact that it is associated with a control device, which cuts the supply of hydraulic fluid if the corresponding clutch is not completely closed.
 19. Hydraulic motor according to claim 18 , characterized by the fact that the multi-disk clutch can be actuated in a hydraulic fashion, and by the fact that the clutch housing (54) contains a hydraulic connection (41).
 20. Hydraulic motor according to claim 18 , characterized by the fact that the control device cuts the supply of hydraulic fluid if the pressure actuating the corresponding clutch does not reach a threshold value.
 21. Hydraulic motor according to one of claim 16 , characterized by the fact that a pinion (7) which is connected to the motor shaft (34) by means of a clutch protrudes out of the clutch housing (54) on the side opposite the motor (51). 